A normally-off hybrid-gate p-GaN high-electron-mobility transistor (HEMT) is presented in this paper. The gate region is designed as a parallel connection between the Schottky-gate and the metal–insulator–semiconductor gate by inserting a dielectric layer under part of the gate metal. Compared to the conventional Schottky-gate p-GaN HEMT, the fabricated hybrid-gate p-GaN HEMT showed a higher threshold voltage of 3.2 V (increases by 167%), and the maximum transconductance is only a slight decrease (reduces by 23%). At the same time, the forward gate leakage current of the hybrid-gate structure is smaller. Furthermore, through simulation, we revealed that the increase in the threshold voltage originated from the delayed full opening of the two-dimensional electron gas. And we also find that the parameters of the gate dielectric layer have a great influence on the performance of the device. The results show that the hybrid-gate structure is a more promising device structure.

The influence of the repair process on the electrical properties of the normally off p-GaN high-electron-mobility transistor (HEMT) is studied in detail in this paper. We find that the etching process will cause the two-dimensional electron gas (2DEG) and the mobility of the p-GaN HEMT to decrease. However, the repair process will gradually recover the electrical properties. We study different repair methods and different repair conditions, propose the best repair conditions, and further fabricate the p-GaN HEMTs devices. The threshold voltage of the fabricated device is 1.6 V, the maximum gate voltage is 7 V, and the on-resistance is 23 Ω·mm. The device has a good performance, which proves that the repair conditions can be successfully applied to the fabricate of the p-GaN HEMT devices.